NEW YORK (CBSNewYork) — A star athlete and student collapsed and died right after football practice on Monday. The 15-year-old had just finished practice drills, when he suddenly could not breathe, or stand up on his own.

“He was the best kid all around. Football-wise, he was the best on the field. He was the nicest kid in general,” teammate Mike Motto said.

“He was the dream kid pretty much,” Frank Vigilante added.

But on Monday Dellaventura’s future was cut short after a hot evening football practice at St. Joseph by the Sea High School on Staten Island. His teammates surrounded him as he collapsed. He later died at the hospital. The cause is still unknown.

“We just saw his face was all blotchy like he said, it would turn purple,” another player said.

“Della was trying his hardest and he just went down,” Motto added.

The team was taking part in a 90-minute conditioning practice that featured no equipment or physical contact. The players said Dellaventura, a powerhouse lineman, never showed any sign of illness during the workout.

“He’s always one to give it his all,” Vigilante said.

“I know he was gonna be sick, be in bad shape. But I didn’t really expect this. None of us did,” Joe Chirelli said.

The bright and talented sophomore was the junior varsity team captain. He also played varsity last year.

“We all are feeling grief and it’s very bad. He’s a big loss for all of us,” one player said.

“He was the nicest kid I ever met in my entire life. I would do anything to have him back,” another teammate said.

Dellaventura’s teammates said they’ll face towering challenges without their star player and team leader, but they’ll dedicate this season to his memory.

Grief counselors will be available at St. Joseph by the Sea High School on Wednesday.